1. Field of the Disclosure
The present application relates to a display device. More particularly, the present application relates to an in-cell touch display device adapted to enhance touch performance.
2. Description of the Related Art
In general, most electrical appliances include a variety of internal and/or external input devices. Each of the electrical appliances inputs commands through the input devices and performs a variety of functions corresponding to the input commands. The input devices are variously implemented according to input modes. Representative examples of the input devices, including a key pad, a mouse and etc., are being used. Recently, touch panels (TSPS) are being increasingly used as the input devices. The touch panel inputs the command by sensing a touch position of a contact object.
The touch panel is disposed on the surface of a display device, such as a cathode ray tube (CRT), a liquid crystal display (LCD) device, a plasma display panel (PDP), an electroluminescent (EL) device or others, in order to sense a touch position of a contact object. An input device using the touch panel can input a command from a user by enabling the user to touch a fixed position of the touch panel with a contact object, such as a finger, a stylus pen or others.
Such a touch panel is classified into an in-cell mode, an on-cell mode and an add-on mode according the combination structure with the liquid crystal panel. The in-cell touch panel is formed within the liquid crystal panel. The on-cell touch panel is formed in an upper layer of the liquid crystal panel. The add-on touch panel is disposed on an outer surface of the liquid crystal panel.
The in-cell touch panel uses a common electrode as a touch electrode. The common electrode used as the touch electrode is divided into a plurality of common electrodes. Such an in-cell touch panel charges the touch electrode with a square wave voltage and compares rising periods of a charging voltage of the touch electrode before and after a touch. The rising period corresponds to a period that the charging voltage of the touch electrode reaches to a previously set voltage.
However, touch line connected to the respective common electrodes, which are used as touch electrodes, must be different from one another in length according to positions of the divided common electrodes. A resistance deviation between the touch lines connected to the respective common electrodes must be generated. The resistance deviation causes touch deviations in accordance with positions of the divided common electrodes. Due to this, reliability of the in-cell touch panel must deteriorate.